Gaucher's disease is an inherited disorder caused by a mutation of the gene for the enzyme glucocerebrosidase. The normal gene for this enzyme has been cloned by several laboratories. We have constructed high-titer, helper-free recombinant retroviruses containing this gene. We have shown that infection of cell lines from normal individuals and patients with Gaucher's disease with this retroviral vector results in increased glucocerebrosidase activity. The glucocerebrosidase gene has been transferred efficiently into progenitor cells and repopulating stem cells of mouse bone marrow, and is expressed at the RNA and protein level in the progeny of CFU-S multipotential progenitor cells following gene transfer. The gene has also been transferred efficiently into murine hematopoietic stem cells that can be used to repopulate secondary transplant recipients. The vector genome can be detected in all hematopoietic lineages and produces human glucocerebrosidase RNA in all hematopoietic tissues tested. High levels of human glucocerebrosidase are generated in hematopoietic tissues. The macrophages of these long-term reconstituted mice produce human glucocerebrosidase levels that are equivalent to the endogenous mouse enzyme levels. Hematopoietic stem cells from rhesus monkeys have been transduced by glucocerebrosidase vector supernatants with a marking efficiency of approximately 1%. The human glucocerebrosidase gene has been introduced into human hematopoietic progenitor cells with a high degree of efficiency. Vector-transduced hematopoietic progenitors from Gaucher patients produce progeny cells with glucocerebrosidase enzyme values similar to those of normal individuals. A clinically acceptable infection protocol has been developed which can be used to correct the enzyme deficiency in hematopoietic cells from Gaucher patients following gene transfer into primitive hematopoietic cells. The first human clinical protocol has started.